Switch to nonblocking I/O, read from stdin.

[cpu]

The original fanotify example program that serves the basis of the rfanotify port uses poll on the fanotify descriptor in nonblocking mode. It also polls stdin to allow the user to quit gracefully by entering any input to stdin.

Presently rfanotify reads from the fanotify descriptor in a blocking fashion. It also doesn't read from stdin or offer any graceful exit, requiring the user to send a signal instead.

I should switch rfanotify to use InitFlags::FAN_NONBLOCK with Fanotify::init and implement an async approach to reading events and monitoring stdin. Since I'm super new to rust I punted on non-blocking I/O in the first version.

[cpu]

I've had luck in a private repo rewriting the Nix bindings to be async using tokio and tokio-fd. I think the resulting changes are much too heavy-weight to be useful to the upstream nix project. For the rfanotify example it might be best to try and rig something up with mio using the existing nix bindings set up with InitFlags::FAN_NOBLOCK.

Guidance here would be welcome. I'm too much of a Rust noob to imagine the best path forward to make the nix bindings small enough to be accepted upstream one day but also flexible enough to allow projects like rfanotify to implement non-blocking reads of events without needing to reinvent the nix bindings with external libraries.